Viscous fan drive systems with fan drive slip feedback

ABSTRACT

A viscous fan drive which includes a moveable component in the scavenge or fill passageway that moves relative to pressure that is proportional to slip speed. The force which moves the component into and out of the passageway is directly proportional to the slip speed of the fan drive. This balances the fill and scavenge flow.

TECHNICAL FIELD

The present invention relates generally to viscous fan drive systems, and more specifically to viscous fan drive systems with improved controllability.

BACKGROUND OF THE INVENTION

The present invention relates to fluid coupling devices for fans, particularly of the type having both a fluid operating chamber and a fluid reservoir chamber, as well as valving which controls the quantity of viscous fluid in the operating chamber.

Although the present invention may be used advantageously in fluid coupling devices having various configurations and applications, it is especially advantageous in a coupling device of the type used to drive a radiator cooling fan of an internal combustion engine, and will be described in connection herewith. It is to be understood, however, that the present invention can be used with other accessories or components and in industrial applications, rather than just with vehicles, such as automobiles and trucks.

Fluid coupling devices of the viscous clutch type, have been used for many years for driving engine cooling fans (thus called “fan drives”). Such fan drives can result in substantial savings of engine horsepower and thus can increase the amount of miles of travel that the vehicle can achieve per gallon of fuel. The typical fluid coupling device operates in the engaged, relatively higher speed condition only when cooling is needed, and operates in a disengaged, relatively lower speed condition when little or no cooling is required.

Electrically activated viscous fan drives are known and used today because they can be controlled between an engaged, partially engaged, and disengaged mode to control output at a given fan speed as determined by the vehicle's engine computer.

Current viscous fan drives, however, often have a mis-match of fill rates to return (or scavenge) flow rates. The control of the fan drive would be improved if the rates of the fill and scavenge flow rates were the same.

Thus, it is an object of the present invention to provide an improved viscous drive for vehicle cooling fans. It is another object of the present invention to provide a viscous fan drive with a system or mechanism which minimizes the fill rate mis-match and thus better controls the fan drive.

SUMMARY OF THE INVENTION

The present invention provides a viscous fan drive mechanism which includes a moveable component that is slip speed dependent and which regulates the amount of passing fluid in a fill or scavenge passageway. This minimizes mis-match between fill and return flow rates by balancing the fill and scavenge flow rates. This results in better control of the fan drive.

The moving component moves relative to pressure that is proportional to slip speed. In a scavenge passageway, the moveable component has a reaction force applied to it due to viscous fluid at a higher pressure from the pumping mechanism (i.e. wiper). The force applied to the moveable component is directly proportional to the slip speed of the fan drive (slip speed is the difference between the input speed and the output speed). With this feedback, the moveable component compensates for differences in slip speed. The compensation causes a varying restriction in the scavenge port flow path.

Low speed reservoir designs can utilize this invention applied to either or both of the return fluid path and the fill fluid path from the fluid reservoir.

The present invention can be utilized with any type of known viscous fan drives, particularly electronically activated viscous fan drives. The actuators can be either the front or rear sides of the fan drives, or the fan drive could be a tetherless design. The reservoirs can be high speed or slow speed, and the fan drive can optionally have a “failsafe” operation or an anti-drain back feature.

Other benefits, features, and advantages of the present invention will become apparent from the following description of the invention, when viewed together with the accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 an exploded view of an embodiment of a known viscous fan drive in which the present invention could be utilized.

FIG. 2 is a perspective partial cross-sectional view of the viscous fan drive as shown in FIG. 1.

FIG. 3 is a cross-sectional view of the viscous fan drive as shown in FIGS. 1 and 2.

FIGS. 4A-4B illustrate the engaged and disengaged positions, respectively, of the valve assembly of the viscous fan drive as shown in FIGS. 1-3.

FIGS. 5A-5D illustrate components of a slip speed sensor and the operation thereof in accordance with the viscous fan drive as shown in FIGS. 1-3.

FIG. 6 depicts an embodiment of the invention in a low pressure, low slip position with low scavenge path resistance.

FIG. 7 depicts an embodiment of the invention in a high pressure, high slip position with high scavenge path resistance.

DESCRIPTION OF PREFERRED EMBODIMENTS

As indicated above, the present invention can be used with virtually any known viscous fan drive. In order to describe the invention and its environment, a preferred embodiment of the invention will be described herein with use with an electronically activated viscous fan drive with a front mounted fan and electrical activation without a tethered harness. The representative viscous fan drive utilized includes an inverted viscous clutch, a drive pulley and a split electromagnetic activator resulting in a mechanical package. An inverted clutch is one in which a conventional clutch is essentially flipped around such that the control shaft is the output shaft while the output members, such as the body and cover, are the input.

Also, the present invention will be primarily described in relation to its use in a scavenge return port and passageway (channel), but it is to be understood that the invention can also be used in the fill path or passageway with substantially the same benefits and effect on controllability of the viscous fan drive.

Referring now to the drawings, which are not intended to limit the invention, FIGS. 1-3 illustrate a representative embodiment of a fluid coupling device 10 (“viscous fan drive”) with which the present invention can be utilized. The device 10 includes a viscous drive mechanism 12 which is utilized to control the speed of rotation of a cooling fan 14. The viscous drive mechanism 12 is attached to a pulley 16 which is operated by a belt (not shown) on the front of a vehicle engine. The fan drive is activated electrically by an electrical coil 18 which is fixedly mounted to a stationary mounting member 20. The mounting member 20 can be a bracket attached to a vehicle engine or the like, or a mounting bracket for a vehicle water pump. A portion of a water pump 22 is shown, for example, in FIGS. 1-3.

The fan member 14 can be any type of fan member known and used today, such as a plastic or metal fan. The fan member 14 is mounted by a plurality of fasteners, such as bolts 15 directly to the rotor member 34 and rotates with it.

The viscous drive mechanism includes a cover plate member 30, a bearing member 32, a rotor member 34, an armature member 36, a reservoir plate member 38 and a body member 40. The body member 40 has a plurality of external fin members 100 which are used to help cool the cover member and the internal components and fluid within the viscous fan drive. The rotor member, reservoir plate member and body member are preferably made from an aluminum material. The cover plate is preferably made from a metal material such as steel. The armature member 36 is preferably made from a plastic material.

Also, as shown in FIG. 3, the cover plate member 30 is fixedly secured to the body member 40. This can be accomplished by a portion of the body member being deformed and swaged over the edge of the cover member, as shown by reference number 31. The body member in turn is directly attached to the pulley member 16 by a plurality of bolts or other fasteners 47.

A rotary seal 42 is used to seal the joint between the cover plate member 30 and the body member 40 to prevent leakage of the viscous fluid adjacent the fan member 14.

A mounting bolt 44 together with a washer 46 (also known as “slinger”), are used to mount the viscous drive mechanism 12 and pulley member 16 to the mounting member 20. The mounting bolt 44 fits within a hollow shaft member 48 which is mounted on the end 49 of the rotating shaft 50, which in this example is a water pump shaft.

The shaft 50 is rotatable mounted within the stationary mounting member 20 by bearing members 52 and 54. The mounting bolt 44 is threadedly mounted to the rotating shaft 50 as shown in FIG. 3.

The electromagnetic system utilized with the representative viscous fan drive mechanism includes a coil 18, along with a steel housing member 19, both of which are mounted to the stationary mounting member 20. The coil 18 has a wire harness 60 that is electrically coupled to a controller 62 and a power source 64. The controller 62 receives electrical signals from a plurality of engine sensors 66 regarding engine and vehicle operating conditions. The operating conditions could be engine temperature, fuel economy, emissions or other engine operating conditions affecting the performance of the engine. For example, one of the sensors 66 could be an engine mounted coolant sensor or a pressure sensor mounted to the air conditioner. The controller 62 has a stored look-up table that determines a desired engine operating range for a given engine speed. When the controller 62 determines that one of more of the sensors 66 are sensing cooling conditions outside the desired operating range, the external controller 62 will direct the power source 64 to send electrical power to the coil 18 as a function of this electrical signal. Thus, for example, if the external controller 62 determines that the engine coolant temperature is too low, or that the engine temperature is too low, a signal may be sent from the controller 62 to the power source 64 to activate the coil 18 to its desired pulse width, therein providing a magnetic field within the fluid coupling device 10.

Similarly, if the external controller 62 determines from one or more of the sensors 66 that the engine, or engine coolant temperature, is above an undesired high range, no signal is sent to the external controller 62 to the power source 64 and coil 18. Thus, in this manner, the controller 62 interprets the signals from the sensor to direct the power source 64 to send or not send electrical current to the coil 18 via the wire harness 60 to control the output from the viscous fan drive 10 in a manner described herein.

As indicated, the stationary mounting member 20 can include a water pump shaft 50 mounted directly to an engine block (not shown) near the crank shaft pulley (not shown) using bolts or other conventional fasteners. In an alternative embodiment (not shown), the water pump mounting bracket can be a stand-alone bracket-pulley subassembly. The water pump shaft 50 is coupled to a plurality of impellers 23 used to control engine coolant flow within an engine cooling system to cool the engine. The water pump shaft 50 is mounted to the pulley 16 through the hollow shaft member 48. Thus, the shaft member 50 rotates at the same rotational rate as the pulley 16 to drive the impellers and therein provide coolant flow to the engine.

As indicated, the pulley 16 is coupled to the engine crankshaft by a drive belt (not shown) and rotates the body member 40 at a rate determined by the engine operating speed translated to the pulley 16 through the crankshaft and belt. The body member 40 has an overlying region 31 that is used to hold the stamped cover plate member 30 fixedly in place in the viscous fan drive. The body member 40 and the cover plate 30 rotate at the same rotational rate as the pulley member 16.

The fan member 14 is rotatably mounted within the viscous fan drive using the ball bearing member 32 and is fixed to the rotor member 34. The rotor member and fan member thus comprise the output of the viscous fan drive.

The volume of space around the rotor member 34 and bounded by the cover 30 and body member 40 defines a fluid reservoir 70 in which a quantity of viscous fluid is provided (not shown). The cover member 30 and reservoir plate 38 define a fluid chamber 72. The volume of space between the radially outer portion of the rotor member 34 and the body member 40 defines the fluid working chamber 74 for the viscous fan drive.

The fluid reservoir 70 is fluidically coupled with the fluid chamber upon movement of the armature member 36 in a manner to be described below. The axial movement of the armature member opens and closes a scavenge fluid flow path depending upon actuation of the electrical coil 18 which controls the flow of fluid between the fluid reservoir and fluid chamber. In addition, the fluid chamber 72 is fluidically coupled to a working chamber 74 which is defined between the outer ends of the rotor member in combination with the body member 40 and cover member 30 in a conventional manner. The amount of viscous fluid contained in the working chamber 74, in conjunction with the rotational speed of the cover and body members coupled to the pulley member 16, determines the torque transmitted to the rotor member 34 that rotates the fan member 14. In other words, the torque response is a result of viscous shear within the working chamber 74. As indicated, the rotation of the fan member is used to cool the radiator or other engine components as required by the engine controller and the appropriate sensors.

In the representative fan drive mechanism, as with most fan drive mechanisms, a rotor member, such as rotor member 34, includes a scavenge system that returns viscous fluid from the working chamber to the reservoir chamber. Disposed adjacent the radially outer periphery of the working chamber is a pumping element also referred to as a “wiper” element. The wiper element operates to engage the relatively rotating fluid in the operating chamber and generate a localized region of relatively higher fluid pressure. As a result, a small quantity of fluid is continuously pumped from the working chamber back into the reservoir chamber through a scavenge channel, such as channel 75.

The armature member 36 has a metal armature ring 37 attached to its outside circumference. (This is better shown in FIG. 5B.) The armature ring 37 is made from a ferrous material. In addition, a multi-pole ring magnet 43 is attached to and part of the armature member 36. The armature ring and multi-pole ring magnet act in combination with the electromagnetic circuitry caused by the coil member 18 to move the armature member in an axial direction along the longitudinal axis of the viscous fan drive system. In this regard, the longitudinal axis is indicated by the centerline 51 (FIGS. 3, 4A, 4B and 5A).

The hub member 39 is made from a ferrous or metal material and is insert cast molded into the body member 40. The hub member has a conical shape with a U-shaped cross-section as shown, in particular, in FIGS. 3 and 4A-4B. After the body member is cast with the hub member in it, an annular channel 53 is formed in the hub member. The channel 53 is in axial alignment with the armature ring 37 on the armature member 36. The space formed by the annular channel 53 provides a working gap in which the armature ring is pulled into and positioned upon actuation of the electromagnetic system.

The armature member 36 is essentially a valve member and operates to open and close the scavenge fluid flow path of the viscous clutch mechanism. This is shown more particularly in FIGS. 4A and 4B. FIG. 4A depicts the valve member in the engaged position and FIG. 4B illustrates the valve member in the disengaged position. In the disengaged position, an opening 80 is provided between the armature member 36 and the reservoir plate member 38 allowing the scavenge fluid flow path to open and the viscous fluid 77A to flow back into the reservoir chamber 70. This disengages the fan member. In the engaged position, the working chamber 74 is filled with viscous fluid and the output members, namely the rotor member 24 and fan member 14, are rotating at full speed or capacity and providing full cooling to the radiator or other engine accessories as needed. In this operational position, the opening 80 is closed and the viscous fluid 77B which is scavenged from the working chamber 74 through scavenge channel 75 to the fluid chamber 72 is recirculated to the working chamber 74.

As a result of the manner in which the fan member is engaged and disengaged, the representative viscous fan drive shown in the drawings is normally in the “on” position. This is known as the “failsafe” condition. In addition, the amount by which the armature member 36 is moved axially and the corresponding amount that the opening 80 is opened regulates the amount of viscous fluid which is returned to the fluid reservoir and the amount which is recirculated to the working chamber. This regulates the speed of the fan member. Thus, the fan member can be in the “on” condition, the “off” condition, and at any rotational speed between those two conditions.

It is also possible with an alternate fan drive embodiment to provide a viscous fan drive which is always in the “off” position and the fan member is only engaged when electrical power is provided and the electromagnetic circuitry is activated. This could be provided with the same structure and components as the failsafe embodiment, but would entail a modification of the programming in the controller 62.

As indicated, the rotor member 34 has a scavenge tunnel 75 which provides a return path for the viscous fluid from the working chamber back into the fluid chamber and/or fluid reservoir.

The flux path for the electromagnetic circuitry is shown by arrows A in FIG. 4B. The flux path A includes the ferrous hub member 39 and the ferrous housing member 19. As indicated, when the sensors 66 indicate to the controller 62 that the rotation of the fan member is not desired or not desired to the same extent, then the coil member 18 is actuated. The actuation of the coil member creates the flux path A, which due to the multi-pole ring magnet 43, moves the armature member axially and positions the armature ring 37 into the channel (or “working gap”) 53.

The amount of electrical power supplied in terms of pulse width modulation from the external controller 62 and power source 64 enhance the amount of magnetic flux available to control the relative positioning of the axially movable armature valve member 36. The controller receives a set of electrical inputs from various engine sensors 66 that monitor various engine operating conditions. The lookup table in the controller determines a desired engine operating range for a given engine speed. When input from one of the sensors to the controller indicates that cooling conditions are outside the desired operating range, the external controller 62 will direct the power source 64 to send electrical power to the coil member 18 as a function of this electrical signal. Thus, for example, if the armature member is pulled or moved axially, a gap is opened between the armature member 36 and the reservoir plate 38 allowing viscous fluid to return to the reservoir 70. This in turn reduces the amount of viscous fluid in the working chamber. Hence, a fan coupled to the output member would rotate slower.

Similarly, if the external controller 62 determines from one or more of the sensors 66 that the engine, or engine coolant temperature, is above an undesired high range, no signal is sent from the external controller 62 to the power source 64 and coil 18. The armature valve member 36 is thus maintained in a position wherein the gap 80 is closed allowing maximum fluid flow from the fluid reservoir 70 to the fluid chamber 72 and to the working chamber 74. This provides maximum torque response of the rotor 34 which in turn rotates the fan member 14 to provide maximum cooling to the radiator to cool the engine coolant.

The representative prior art fan drive 10 shown in the drawings utilizes for comparison purposes an integrated slip speed sensor which is not necessary with the present invention. The integrated slip speed sensor shown in FIGS. 5A-5D includes additional components which are expensive and which add complexity to the fan drive. The sensor monitors the clutch output speed with an electromagnetic circuit partially comprised of components common with the clutch. The circuit configuration provides a speed sensor that measures the speed differential between the clutch output and the clutch input. When measured by the controller (or a remote computer), the differential speed is subtracted from the clutch input speed to determine the output speed.

For the electromagnetic circuit, a sensor pole member 41, along with a Hall Effect Device (HED) 110, or another magnetic sensing device as provided. The HED 110 is positioned on the end of a flux concentrator 111 which is attached to the coil member 18. There are shown more particularly in FIGS. 5C and 5D, in combination with FIG. 5A which depicts the flux path B of the slip speed sensor system. The pole member 41 has a plurality of magnetic poles 112 arranged circumferentially around the inside of an outer ring 114. The flux path B includes the HED sensor 110, the hollow shaft member 48, the ring magnet 43, the pole member 41 and the hub member 39.

The ring magnet pole member 41 rotates at input speed relative to the stationary HED 110. The alternating poles of the ring magnet 41 create alternating directions of the magnetic flux in the magnetic circuit proportional to the differential speed of the input and output. The differential speed is determined by the difference in speed between the pole member 41 and ring magnet 43.

An embodiment of the present invention is shown in FIGS. 6 and 7 and provides a mechanism and system that has a moveable member that is dependent on slip speed. The invention renders unnecessary the slip speed sensor system described above. As indicated, the slip speed is the difference between the input speed of the fan drive and the output speed. A preferred embodiment of the invention includes a mechanism 200 which is positioned in a passageway 212 that is in fluid communication with the scavenge channel 214. The scavenge channel can be, for example, scavenge passageway 75 in the viscous fan drive embodiment described above and shown in FIGS. 3, 4, 4A and 5A.

In FIGS. 6 and 7, the flow of fluid in viscous fan drive between the working chamber and the scavenge passage is shown by arrow 220. The primary velocity of the clutch plate (i.e. the input speed) is shown by the arrow V_(P). The secondary velocity of the body and cover, i.e. the output speed, is shown by arrow V_(S). The wiper member 222, which is also a pumping mechanism, is shown in its conventional position diverting fluid flow into the scavenge channel. The difference between the two velocities V_(P) and V_(S) and the resultant pressures P_(L) and P_(H) is directly portioned to the slip speed.

The moveable member 210 is biased by coil spring member 216 in a direction shown by arrow 217 so that the member does not protrude into the scavenge passageway 214 through port 230 under low pressure (low slip) conditions. In this situation as shown in FIG. 6, the pressure P_(L) is low due to a low amount, such as a minimal amount, of slip. The resistance in the scavenge channel 214 is low.

In high pressure situations where there is a significant amount of slip, the pressure P_(H) in the scavenge channel 214 is high. This creates high resistance in the scavenge path and sufficient force from the fluid flow in passageway 212 to overcome the force of the spring biasing member and cause the moveable member 210 to protrude into the scavenge channel through port 230.

The amount of spring force necessary in any viscous clutch embodiment will depend on the size and construction of the viscous clutch, as well as the calculated or measured high and low pressures in the scavenge passageway. The spring force is preferably appropriate to allow the moveable member to balance, or substantially balance, the flows in the scavenge and fill passageways.

The moveable member 210 has a base or body portion and a smaller protrusion portion. The base portion is larger than the protrusion portion. This is shown in the drawings.

The amount of protrusion of the member 210 into scavenge channel is dependent on the amount of fluid pressure and thus directly dependent on the amount of slip speed. The moveable component compensates for differences in the slip speed and acts to balance the flow in the fill and scavenge passageways. The compensation is in the form of a varying restriction in the scavenge flow path. This regulates the fluid flow in the scavenge passageway returning fluid to the reservoir and, in turn, improves the controllability of the viscous fan drive.

As indicated, the moveable member moves into and out of the scavenge channel relative to a pressure which is proportional to the slip speed. The movement of the moveable member in the representative embodiment shown is caused by mechanical feedback which compensates for differences in slip speed. For optimum controllability of a viscous fan drive at all operating conditions, it is preferable that the fill and scavenge rates be the same, or substantially the same.

The amount of movement of the moveable member 210 can also be read by a conventional sensor 232 and relayed directly to the electronic control unit (ECU) of the vehicle, although this may be redundant or unnecessary. The ECU could utilize these parameters and adjust the amount of fluid passaging through the fill and scavenge ports from and into, respectively, the reservoir.

In an alternate embodiment of the invention, the moveable member could be positioned in the fill passageway or channel leading from the reservoir to the working chamber. Low speed reservoir designs, in particular, could benefit from this embodiment.

While preferred embodiments of the present invention have been shown and described herein, numerous variations and alternative embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention is not limited to the preferred embodiments described herein but instead limited to the terms of the appended claims. 

What is claimed is:
 1. A viscous fluid coupling assembly for a fan member comprising: an output member including a center shaft and configured for attachment to a fan member; an input member bearing mounted to said output member and rotatable relative to said output member and at input speed; a viscous fluid supply mechanism positioned within said input member and comprising a rotor member, a reservoir plate member having a fluid aperture, a fluid reservoir, a scavenge passage, a wiper, a working chamber and a quantity of viscous fluid; a valve mechanism for controlling viscous fluid engagement of said output member with said input member, said valve mechanism having a moveable member for opening, partially opening and covering said fluid aperture; and a moveable member positioned in operative association with said scavenge passage; said moveable member being moveable into and out of said scavenge passage and being able to alter the flow of viscous fluid in said scavenge passage; said moveable member being moveable relative to pressure that is proportional to slip speed.
 2. The viscous fluid coupling assembly of claim 1 further comprising an electronic control for controlling the movement of said valve mechanism.
 3. The viscous fluid coupling assembly of claim 1 wherein said output member comprises a housing and said input member comprising a body member and a cover member.
 4. The viscous fluid coupling assembly of claim 3 wherein said input member is positioned around said output member and rotates at input speed.
 5. The viscous fluid coupling assembly of claim 1 wherein said moveable member is moveable into said scavenge passage through an opening in said passage.
 6. The viscous fluid coupling assembly of claim 5 further comprising a biasing member biasing said moveable member away from entering said scavenge passage.
 7. The viscous fluid coupling assembly of claim 1 further comprising a secondary passageway which is in fluid communication with said scavenge passageway and which applies fluid pressure to said moveable member.
 8. A viscous fluid coupling assembly for a fan member comprising: an output member including a center shaft and configured for attachment to a fan member; an input member bearing mounted to said output member and rotatable relative to said output member and at input speed; a viscous fluid supply mechanism positioned within said input member and comprising a rotor member, a reservoir plate member having a fluid aperature, a fluid reservoir, a scavenge passage, a fill passage, a wiper, a working chamber and a quantity of viscous fluid; a valve mechanism for controlling viscous fluid engagement of said output member with said input member, said valve mechanism having a moveable member for opening, partially opening and covering said fluid aperature; and a moveable member positioned in operative association with said fill passage; said moveable member being moveable into and out of said fill passage and being able to alter the flow of viscous fluid in said fill passage; said moveable member being moveable relative to pressure that is proportional to slip speed.
 9. The viscous fluid coupling assembly of claim 1 wherein said moveable member is moveable into said fill passage through an opening in said passage.
 10. The viscous fluid coupling assembly of claim 9 further comprising a biasing member biasing said moveable member away from entering said fill passage.
 11. The viscous fluid coupling assembly of claim 1 further comprising a secondary passageway which is in fluid communication with said fill passageway and which applies fluid pressure to said moveable member. 